Energy absorbing type occupant protection systems in automobiles, such as the collapsible steering column described in U.S. Pat. No. 3,392,599, issued July 16, 1968 to R. L. White and assigned to the assignee of this invention, absorb or dissipate energy by stroking a first member relative to a second member against a resisting force developed between the two members. With respect to minimizing the reaction force experienced by an occupant initiating an energy absorbing stroke between the two members, optimal performance is achieved when the kinetic energy of the occupant just matches the energy absorbing capacity of the system, i.e the kinetic energy of the occupant is fully expended just a completion at the maximum stroke between the members. In typical energy absorbing occupant protection systems where the energy absorbing capacity is fixed at the time the system is assembled, optimal performance is difficultl to achieve because the amount of energy the system must absorb depends on variables such as the mass of the occupant. In an occupant protection system according to this invention, the energy absorbing capacity of the system is actively adjusted in accordance with a least one operational variable so that the performance of the system in an actual energy absorbing event is more likely to aapproach optimal performance.